INP spans sent via tunnel fail because they are missing the expected "dsn" property #12094

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/browser

SDK Version

8.2.1

Framework Version

No response

Link to Sentry event

No response

SDK Setup

No response

Steps to Reproduce

I enabled the tunnel option pointing at my tunnel controller, which looks for a dsn property in the first part of the payload. This has always worked fine with v7, and I believe is correct according to the tunnel docs at https://docs.sentry.io/platforms/javascript/troubleshooting/

On v8, the dsn property is missing for INP spans. Seems like this is a bug in v8? Or else, tunnels would need to be modified to work without receiving the "dsn" property.

Expected Result

On v7, the tunnel payload for INP spans looks like this (note the dsn property):

{"sent_at":"2024-05-17T03:57:01.321Z","dsn":"https://foo@ingest.us.sentry.io/bar"}
{"type":"span"}
{"data":{"sentry.origin":"manual","sentry.op":"ui.interaction.click"...

Actual Result

On v8 the tunnel payload is missing the dsn property:

{"sent_at":"2024-05-17T04:04:23.208Z","trace":{"trace_id":"c13cef34cd1248b3917969b9f20c4acb","sample_rate":"1","transaction":"GET /node","public_key":"foo","environment":"prod","sampled":"true"}}
{"type":"span"}
{"data":{"sentry.origin":"manual","sentry.op":"ui.interaction.click"...